Nevertheless, slice resource reservation raises several challenging
problems: Slice requests are submitted by Service Providers (SPs)
at different time instants, with various activation delays, life durations,
and user demands fluctuating with time. The variety of services supported
by slices induces very different Quality of Service (QoS) requirements
[1]}. Moreover, various constraints may be imposed by the
different network segments on which slices have to be deployed [2]}, [3]}.
For example, coverage constraints are imposed by slices involving
the radio access network [4]}. Additionally, several
sources of uncertainty have to be considered in a reservation approach,
e.g., the number of slice users, the hardly predictable user
locations [5]}, and the time-varying per-user resource
requirements. Consequently, enough infrastructure resources should
be reserved for each slice to guarantee an adequate QoS specified
in the SLA and provide robustness against uncertainties. Too many
infrastructure resources should not be reserved too, in order to reduce
costs and leave resources to concurrent slices.
